Tool orienting method and apparatus



2 Sheets-Sheet l fifa f ya.

D. HERING TOOL ORIENTING METHOD AND APPARATUS Filed Dec. 25, 1942 Aug.12, 1947.

Aug. l2, 1947. D, HERING I TOOL .ORIENTING METHOD AND APPARATUS FiledDeo. 25, 1942 2 sheets-sheet 2 9 ll Il wrm/7m? a /c/ er? l? Za y//Patented Aug. 12, 1947 TOOL ORIENTING METHOD AND APPARATUS DonaldHering, Long Beach, Calif., assignor to Sperry-Sun Well SurveyingCompany, Philadelphia, Pa., a corporation of Delaware ApplicationDecember 23, 1942, Serial No. 469,867

20 Claims. (Cl. Z55-1.0)

This invention relates to a method and apparatus for orienting drillstems, and more particularly to a method of orienting drill stems forthe Purpose of directional drilling.

There is disclosed in Hyer Patent 2,120,670, dated June 14, 1938, amethod of orienting drill stems, especially for the purpose of orientingtools, which has been widely and satisfactorily used. In accordance withthis method, all mechanical interconnections between a surveyinginstrument and drill stem are avoided, the operative interconnectionbetween a surveying instrument and the drill stem being effected throughthe medium of a magnet located in a portion of the drill stem andadapted to attract a compass within a surveying instrument, desirably ofa recording type. Somewhat similar methods of orientation are describedin the patents to Hewitt et al, 2,144,061 and 2,154,162, dated,respectively, January 17, 1939, and April 11, 1939, in the patents toSmith 2,179,832 and 2,187,367, dated, respectively, November 14, 1939,and January 16, 1940, and to Bremner et al. 2,207,505, dated July 9,1940, and in the application of Smith, Serial No. 414,160, iiled October8, 1941.

All of these orienting methods involve in common the lowering into a,drill stem of a recording surveying instrument the records of which arerelated in some fashion with a direction of asymmetry of a tool. Thefact that the instruments are of recording type involves the necessityfor lowering the instrument in each case to a predetermined location inthe drill stem, permitting it to remain there for a sufficient time tomake a record, withdrawing the instrument from the drill stem, removingand examining the record, and only then locating the drill stem in suchposition as to face the tool in the proper direction. During the periodof withdrawal of the instrument, it is not necessary that the drill stembe stationary provided suitable markings are made at the surface toindicate the position of the drill stem at the time the record was beingmadeby the surveying instrument. In general, however,

the ruiming of the instrument into the drill stem,

its removal and the development and examination of the recordnecessitated a substantial loss of time during which drilling progressmust be interrupted.

It is the general object of the present invention to provide an improvedorienting method and apparatus whereby the same fundamental principlesare involved as in the various methods and apparatus of theaforementioned patents and application, but nevertheless the. time con-`sumed is substantially shortened by reason of the fact that theinstrument, instead of making a record, is adapted to signal to thesurface the condition of orientation which has been achieved.

Specifically, in accordance with the present invention, there is loweredinto the drill stem to a point adjacent its lower end carrying a tool asurveying instrument which will signal to the surface the relationshipbetween a magnet located in definite azimuthal position relative to the`tool and an azimuthal reference direction which may be, for example,the known direction of inclination of the hole.

The general object just indicated, as well as specic objects 0f theinvention relating to details, will become apparent from the followingdescription, read in conjunction with the accompanying drawing, inwhich:

Figure 1 is a longitudinal sectional view showing the assembly of partsattained at the time the surveying instrument is signalling theorientation data to the surface;

Figure 2 is an enlarged longitudinal section through the drill stem andthe surveying instrument therein showing certain of the operating partsthereof;

Figure 3 is a diagram showing primarily the electrical connections ofthe apparatus and indicating certain of the mechanical relationships ofthe parts; and

Figure 4 isa plan View showing the type of indicating device located atthe surface and from which the orientation may be ascertained.

A drill stem made up of sections in the usual fashion carries in itslower portion a sub indicated at 2 above the bit and the tool, hererepresented as a whipstock 1, carried by the lower end of the drill stemby means of a shear pin in usual fashion. The assembly thus illustratedis conventional and may involve the more elaborate assembly of partsillustrated in the patent to Kothny 2,298,706, dated October 13, 1942.

The sub 2 m-ay be formed of either magnetic or non-magnetic material,depending upon the particular type of interior apparatus used. In themodification illustrated, this sub may be of steel or other magneticmaterial and carries a, magnet 4 located within plug 6 of non-magneticmaterial such as bronze or the like, serving to separate the magneticmaterial of the sub from the magnet so that the field of the magnet isnot suppressed and extends to a substantial degree within the opening inthe drill stem. f

Arranged to be lowered within the drill stem upon a cable which, in thepresent instance may contain a single conductor, though additionalconductors may be provided if it is desired to transmit electrical powerfrom the surface, is a protective casing 8, adapted to seat on a ring g,as indicated in Figure 1, within which protective casing there islocated a surveying instrument ID of novel type. The devices within thesurveying instrument are partially indicated in physical form in Figure2 and diagrammatically in Figure 3. They comprise a motor I2 having ashaft I4 preferably of tubular form. This tubular shaft carries a pairof coils I6 and I8, located at different levels and electricallyconnected in series, one end of the coil I8 being grounded as indicatedat 24 through the shaft and its bearings. The coils I6 and I8 arepreferably carried by members 20 and 22, respectively, of Sofit iron forthe purpose of minimizing the reluctance of the magnetic circuitshereafter described, thereby to promote the generation of a maximuminduced electromotive force. The lead from the upper coil I6 iselectrically joined through a brush 26 to a conductor 28 in the cablewhich supports the surveying instrument and runs to the surface, Theupper end of this conductor is connected (for example through aconventional slip ring and brush arrangement) to the input transformeri2B of a push-pull amplifier 42. It will be evident that a single coilmay be used instead of the pair I6, I8 if proper precautions are takento avoid any conflict of the fields of the magnets 4 and 34 such asmight cause 34 to be attracted by magnet 4 to an incorrect position,

The motor I2 is arranged to be driven by means of a battery 30 containedin the surveying instrument, though if desired, it may be driven by theintroduction of power current through another conductor in thesupporting cable, though with suitable ltering the power may besupportedthrough the same cable which transmits the impulses. If abattery 30 is used, as is convenient since the motor l2 may be of quitesmall size, it is desirable to provide in the motor circuit a mercuryswitch 32 arranged to make contact only when the instrument issubstantially upright within the normal deviations of a hole from thevertical, so that the motor will be run and tend to drain the batteriesonly when the surveying instrument is in use, the instrument at othertimes being desirably kept in a substantially horizontal position.

Adjacent the lower coil I8 there is arranged a means for indicating aknown azimuthal reference direction comprising a magnet 34 mounted in auniversal pivot 35, the upper end of the magnet indicated at 4i) closelyapproaching the path of rotation of the lower turns of the coil I 8.Surrounding the upper end of the magnet 34 is a disc 38 of non-magneticmaterial which will bear against the inner wall of the surveyinginstrument casing I and, when the instrument is inclined to thevertical, will seek the lowermost portion of that wall, so indicating aknown azimuthal reference direction.

The output of the push-pull amplifier 42 is fed to brushes makingcontact with slip rings 44 land 46, which are in turn electricallyconnected to the electrodes 52 and 54 of a glow tube 50 of the commonneon or argon type. The slip rings 44 and 46 are carried by a verticalshaft 48 to an arm 49 of which the glow tube is secured at a substantialdistance from the axis of rotation, desirably with the electrodesarranged as indicated in Figure 4, i. e., at different distances fromthe axis of rotation with the separating region. be-

tween them extending substantially circumferentially. The connectionsbetween the slip rings and the electrodes are, of course, made throughor along the shaft 43. The shaft 48 is arranged to be driven by means ofa motor 56, the speed of which is adjustable, for example, through themedium of a rheostat 5S. As will be evident hereafter, the range ofspeed adjustment of the motor 56 should be such as to correspond withthe normal range of speed of the motor I2, the speed of which may varyas the batteries 30 are drained. The speed of this motor is not at allcritical, and it may be of an ordinary small direct current type. Allthat is necessary is that it should be possible to operate the motor 5Bat essentially the same speed at the time of performing an orientation.

The glow tube 50 is arranged to rotate adjacent a compass rose orazimuth circle indicated at 60, which carries graduations 62 indicativeof azimuthal directions. If the compass rose is provided on a glassCover plate over the rotating glow tube and associated parts, this platemay also desirably carry a circle 64 coincident, during the rotation,with the region dividing the electrodes 52 and 54, This makes itpossible more readily to distinguish the ashes of the electrodes whichare inside and outside the circle 64 and hence to be distinguished fromeach other.

In the use of the apparatus described, the instrument contained in theprotective casing 8 is lowered into the drill stem carrying thefwhipstock "a at its lower end which, at the time, will have an unknownorientation and will be located at the bottom of the bore hole generallyslightly above the lower end thereof. As the instrument passes down thedrill stem, the motor I2 will operate to spin the pick-up coils I6 andI8, the latter through the field of the magnet 34 which, during thedescent, will, of course, oscillate about the axis of the instrument sothat the indications at the surface will be meaningless. When theinstrument comes to rest on the supporting shoulder, the coil I6 will berotating opposite the magnet 4, so as to cut its field, and the magnet34 will then come to a rest position with its disc 38 engaging thelowermost side of the housing Iii, assuming the hole to be sloping evenslightly at the position of the whipstock.

The position of the magnet 4 with respect to the condition of asymmetryof a tool (for example, the direction of the face of a whipstock) havingbeen noted at the surface during assembly, it will be evident that fromthis, an indication of the angular relationship between magnets 4 and 34and a knowledge of the direction of slope of the hole from a previoussurvey, the azimuthal position of the tool may be ascertained. Thedirection of slope with respect to the earth need, however, not be knownif the straightening or deviation to be effected is only to be relativeto the low side of the hole, so that in some cases, the results of aprevious survey are unnecessary. The apparatus determines the angularrelationship -between the magnets as follows:

The push-pull amplifier 42 is so designed that the two symmetrical partsthereof are normally biased to cut-off, with the result that pulses ofvoltage will be applied to the outer electrode 52 and the innerelectrode 54 individually corresponding to the cutting of the respectivemagnetic fields by the coils I6 and I8. For the sake of simplicity, letit be assumed that the electrode 52 is energized by the pulses producedin the coil I6 and the electrode 54 is energized by the pulses producedin the coilv I8, these coils being wound in proper relationship to thepolarity of the magnets that the induced electromotive forces of thepulses are opposite in sign, If a single coil is used the magnets willIbe correspondingly arranged so as to give opposite pulses.

Before adjusting the rheostat 58, if the speed of the motor 55 dii'lersfrom that of the motor I2,v there will thus be produced stroboscopicflashes of light travelling forwardly or 4backwardly about thecompassrose on the opposite Sides of the circular line 64. If, now, the speedof the motor 56 is adjusted to correspond with the speed of rotation ofthe motor I2, the ilashes will become stationary, the attainment of thiscondition indicating, of course, that the two motors do correspond inspeed (assuming that it is known that they run approximately at the samespeed.)

From previous surveying of the hole, there will be known the azimuthaldirection of the inclination of the hole. The setting of the rheostat 53may'now be slightly changed so as to cause the motor 56 to have a speedeither slightly greater or slightly less than that of the motor i2, withthe result that flashes of the electrode 54 will progress slowly aroundthe compass rose until they appear at the azimuthal positioncorresponding to the -direction of deviation of the hole, whereupon therheostat 58 may be again adjusted to attain a constant speed of themotor 5S corresponding to that of the motor I2 to cause the flashes tovappear stationary. This stationary condition of the dashes of theelectrode 54 is indicated at 68 and will result in a streak of lightslightly longer than the circumferential dimension ofthe electrode inView of the fact that the pulse persists through a small angularmovement of the coil I8 and the electrode 54. Alternatively, anarbitrary stationary position of the ilashes may be secured and thecompass rose then rotated to the aforesaid position,

At this same time, the flashes of the electrode 52l will appear as asimilar short streak of light at 66 which will also be stationary andwhich will indicate the position of the magnet 4. Since the magnet 4bears a known relationship to the direction in which the sloping face ofthe whipstock points, there may thus be directly determined from theposition of the iiashes 68 with respect to the compass rose thedirection in which the whipstock is then facing.

It will be evident that the convention adopted in the arrangement of thevarious parts is rather arbitrary. With various relative positions ofthe .coils I8 and I6 with respect to each other about Y the shaft I4 andcorresponding positions of the magnet 4 with respect to the whipstockface, as well as the arrangement within the amplifier itself, thedirection in which the whipst'o-ck faces may be directly indicated onthe rose. The arrangement and conventions used must, of course, be tiedup with the particular arrangement of the various parts of the apparatusas just indicated.

If it is desired to face the whipstock in some other direction, thedrill stem is now turned at the surface through the proper angle,preferably accompanied by spudding, and upon readjustment, the motor 55may be again speeded up or slowed down to bring the ilashes 53 again tothe direction on the compass rose corresponding to the direction of theinclination of the hole, or alternatively, the compass rose may berotated to achieve this condition. The flashes 66 -will then againindicate the position of the whipstock in its newly adjusted location.If the turning of the drill stem failed to achieve the desired position,the operation may 4be repeated until the whipstock is indicated asfacing in the proper direction.

Following the attainment of the proper azimuthal position of thewhipstock, pressure may be applied by release of the drill stem at thesurface to drive the lower end of the whipstock into the earth and shearthe pin securing the whipstocl: to the drill stem. As the shearing takesplace, the apparatus will continue to indicate the azimuthal position ofthe whipstock, with the result that there is complete assurance that thewhipstock has been set in the desired direction.

Thereupon the drilling may be immediately started by rotation of thedrill stem with the conventional hook-up, the instrument being withdrawnduring the drilling operation. Mud circulation may, of course, beprovided by having the supporting cable pass through a suitable stuffingbox arrangement, the circulation being interrupted only when it isnecessary to remove the instrument upon its arrival at the surface.

It will =be noted that the mere act that the twoiiashes appear is acheck upon the location of the instrument at a position with the coil I6opposite the magnet 4, since, as soon as this coil is slightly removedfrom the region of the magnet, the flashes of the electrode 52 willcease. Thus a direct indication of the position of the whipstock and theproper operation of the apparatus are both dei'initely assured.

A cathode ray tube may be used to advantage l in place of thearrangement described if the sweep voltage is controlled as tofrequency. Many types of detecting apparatus may be provided to securethe identical fundamental effects.

In the above description it has been assumed that the azimuth isdetermined by means of a member responsive to the slope of the holes.The azimuth may, however, be indicated directly by arranging coil it asthe coil of an earth inductor compass, in which case it should be wellremoved from magnet 4 so as to respond to the undisturbed earths eld,the instrument, its casing, and the sub of the drill stem being in thiscase of non-magnetic material. Alternatively, the coil may be affected'by a pole of a compass needle which is arranged to respond to theearths magnetic field. Or in still another arrangement, a magnetarranged to effect induction of pulses in the coil may be carried by agyroscope to give a positive indication of direction.

What I claim and desire to protect by Letters Patent is:

l. The method of orienting a tool within a bore hole including loweringthe tool into the bore hole on a hollow drill stem, the lower portion of.which drill stem carries a magnetic element, lowering within the drillstem an instrument containing means for indicating a known azimuthalreferencev direction and means responsive to the magnetic fieldestablished by said magnetic element for` transmitting to the surfaceindications of the relationship of, the magnetic element to the azimuthindicating means, and rotating the drill stem to bring the tool into apredetermined azimuthal position upon noting said transmittedindications.

2. The method of orienting a tool within a bore hole including loweringthe tool into the bore hole on a hollow drill stem, the lower portionofA which drill stem carries a magnetic element, lowering within thedrill stem an instrument containing means for indicating a knownazimuthal reference 7 direction and means responsive to the magneticfield established by said magnetic element for transmitting to thesurface indications of the relationship of the magnetic element to theazimuth indi-eating means, and rotating the drill stem to bring the toolinto a predetermined azimuthal position upon noting said transmittedindications, said indication transmitting means comprising devices fortransforming the indications into electromagnetically induced impulses.

3-. The method of orienting a tool within a bore hole including loweringthe tool into the bore hole on a hollow drill stem, the lower portion ofvwhich drill stem is provided with means bearing a predeterminedrelationship to the tool carried thereby, lowering within the drill steman instrument containing means for indicating a known azimuthalreference direction and means responsive to the location of the iirstmentioned means for transmitting to the surface indications of therelationship of said means at the lower portion of the drill stem to theazimuth indicating means, and rotating the drill stem to bring the toolinto a predetermined azimuthal position upon noting said transmittedindications, said indication transmitting means comprising devices fortransforming the indications into electromagnetically induced impulses.

4. The method of orienting a tool Iwithin a bore hole including loweringthe tool into the bore hole on a hollow drill stem, the lower portion ofwhich drill stem carries a magnetic element, lowering within the drillstem an instrument containing means for indicating a known azimuthalreference direction and means responsive to the magnetic eld establishedby said magnetic element for transmitting to the surface pulsesindicative of the relationship of the magnetic element to the azimuthindicating means, detecting the relationship of the transmitted pulsesby means of a stroboscopic apparatus, and rotating the drill stem tobring the tool into a predetermined azimuthal position.

5. The method of orienting a tool within a bore hole including loweringthe tool into the bore hole on a hollow drill stem, the lower portion ofwhich drill stem is provided with means bearing a predeterminedrelationship to the tool carried thereby, lowering within the drill steman instrument containing means for indicating a known azimuthalreference direction and means responsive to the location of the nrstmentioned means for transmitting to the surface periodic pulsesindicative of the relationship of said means at the lower portion of thedrill stem to the azimuth indicating means, detecting the relationshipof the transmitted pulses by means of a stroboscopic apparatus, androtating the drill stem to bring the tool into a predetermined azimuthalposition.

6. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of the drill stem;and an instrument arranged to pass through the drill stem and arrangedto occupy a predetermined final longitudinal position therein adjacentthe tool and said magnetic element, said instrument containing means forindicating a known azimuthal reference direction and means responsive tothe magnetic eld established by said magnetic element for transmittingto the surface indications of the relationship of the magnetic elementto the azimuth indicating means.

'7. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of the drill stem;an

instrument arranged to pass through the drill stem and arranged tooccupy a predetermined final longitudinal position therein adjacent thetool and said magnetic element, said instrument containing means forindicating a known azimuthal reference direction and means responsive tothe magnetic field established by said magnetic element for transmittingto the surface pulses indicative of the relationship of the magneticelements to the azimuth indicating means; and a stroboscopic apparatusfor detecting the relationship of the transmitted pulses.

8. In combination, a hollow drill stem; a tool carried by the drillstem; meansI provided at the lower portion of the drill stem bearing apredetermined relationship to the tool carried thereby; an instrumentarranged to pass through the drill stem and arranged to occupy apredetermined nal longitudinal position therein adjacent the tool andsaid means, said instrument containing means for indicating a knownazimuthal reference direction and means responsive to the location ofthe first mentioned means for transmitting to the surface pulsesindicative of the relationship of said means at the lower portion of thedrill stem to the azimuth indicating means; and a stroboscopic apparatusfor detecting the relationship of the transmitted pulses.

9. In combination, a hollow drill stem; a tool carried by the drillstem; means provided at the lower portion of the drill stem bearing apredetermined relationship to the tool carried thereby; an instrumentarranged to pass through the drill stem and arranged to occupy apredetermined nal longitudinal position therein adjacent the tool andsaid means, said instrument containing means for indicating a knownazimuthal reference direction, and means responsive to the location ofthe rst mentioned means for transmitting automatically periodically tothe surface pulses indicative of the relationship of said means at thelower portion of the drill stem to the azimuth indicating means; and astroboscopic apparatus for detecting the relationship of the transmittedpulses.

10. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of the drill stemand bearing a predetermined relationship to the tool carried thereby; aninstrument arranged to pass through the drill stem and arranged tooccupy a predetermined inal longitudinal position therein adjacent thetool and said magnetic element, said instrument containing means forindicating a known azimuthal reference direction and means responsive tothe magnetic field established by said magnetic element for transmittingautomatically periodically to the surface pulses indicative of therelationship of said magnetic element at the lower portion of the drillstem to the azimuth indicating means; and a stroboscopic apparatus fordetecting the relationship of the transmitted pulses.

11. In combination, a hollow drill stem; a tool carried by the drillstem; means provided at the lower portion of the drill stem bearing apredeterminedrelationship to the tool carried thereby; an instrumentarranged to pass through the drill stem and arranged to occupy apredetermined final longitudinal position therein adjacent the tool andsaid means, said instrument containing means for indicating a knownazimuthal reference direction and means responsive to the location ofthe first mentioned means for transmitting automatically periodically tothe surface electromagnetically induced pulses indicative of therelationship of said means at the lower portion of the drill stem to theazimuth indicating means; and a stroboscopic apparatus for detecting therelationship of the transmitted pulses.

12. In combination, a hollow drill stem; a tool carried by th'e drillstem; a magnetic element carried by the lower portion of the drill stemand bearing a predetermined relationship to the tool carried thereby; aninstrument arranged to pass through the drill stem and arranged tooccupy a predetermined final longitudinal position therein adjacent the'tool and said magnetic element, said instrument containing means forindicating a known azimuthal reference direction, and means responsiveto the magnetic eld established by said magnetic element fortransmitting automatically periodically to the surfaceelectromagnetically induced pulses indicative of the relationship ofsaid magnetic element at the lower portion of the drill stem to theazimuth indicating means; and a stroboscopic apparatus for detecting therelationship of the transmitted pulses.

13. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of the drill stem;and an instrument arranged to pass through the drill stem and arrangedto occupy a predetermined nal longitudinal position therein adjacent thetool and said magnetic element, said instrument containing means forindicating a known azimuthal reference direction, and means responsiveto the magnetic field established by said magnetic element forautomatically periodically transmitting to the surfaceelectromagnetically induced pulses indicative of the relationship of themagnetic element to the azimuth indicating means.

14. In combination, a hollow drill stem; a tool carried by the drillstem; means provided at the lower portion of the drill stem bearing apredetermined relationship to the tool carried thereby; and aninstrument arranged to pass through the drill stem and arranged tooccupy a predetermined flnal longitudinal position therein adjacent thetool and said means, said instrument containing means for indicating aknown azimuthal reference direction and means responsive to the locationof the rst mentioned means for automatically periodically transmittingto the surface electromagnetically induced pulses indicative of therelationship of said means at the lower portion of the drill stem toth`e azimuth indicating means.

15. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of the drill stemand bearing a predetermined relationship to the tool carried thereby;means for indicating a known azimuthal reference direction, and meansresponsive to the magnetic field established by said magnetic elementfor transmitting to the surface electromagnetically induced pulsesindicative of the relationship of the magnetic element to the azimuthindicating means.

16. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of th'e drill stemand bearing a predetermined relationship to the tool carried thereby;means for indicating a known azimuthal reference direction, and meansresponsive to the magnetic eld established by said magnetic element forautomatically periodically 10 transmitting to the surface pulsesindicative of the relationship of the magnetic element to the azimuthindicating means.

17. In combination, a hollow drill stem; a tool carried by the drillstem; means provided at the lower portion of the drill stem bearing apredetermined relationship to the tool carried thereby; means forindicating a known azimuth'al reference direction, and means responsiveto the location of the first mentioned means for transmitting to thesurface electromagnetically induced pulses indicative of therelationship of said means at the lower portion of the drill stem to theazimuth indicating means.

18. In combination, a hollow drill stem; a tool carried by the drillstem; means provided at the lower portion of the drill stem bearing apredetermined relationship to the tool carried thereby; means forindicating a known azimuth reference direction, and means responsive tothe location of the rst mentioned means for automatically periodicallytransmitting to the surface pulses indicative of the relationship ofsaid means at the lower portion of the drill stem to the azimuthindicating means.

19. In combination, a hollow drill stem; a tool carried by the drillstem; a magnetic element carried by the lower portion of the drill stemand bearing a predetermined relationship to the tool carried thereby;means for indicating a known azimuthal reference direction; meansresponsive to the magnetic field established by said magnetic elementfor automatically periodically transmitting to the surface pulsesindicative of the relationship of the magnetic element to the azimuthindicating means; and a stroboscopic apparatus for detecting therelationship of the transmitted pulses.

20. In combination, a hollow drill stem; a tool carried by the drillstem; means provided at the lower portion of the drill stem bearing apredetermined relationship to the tool carried thereby; means forindicating a known azimuthal reference direction; means responsive tothe location of the rst mentioned means for automatically periodicallytransmitting to the surface pulses indicative of the relationship ofsaid means at the lower portion of the drill stem to the azimuthindicating means; and a stroboscopic apparatus for detecting therelationship of th'e transmitted pulses.

DONALD HERING.

REFERENCES CTED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,209,102 Anschutz-Kaempfe Dec.19, 1916 1,928,970 Johnston Oct. 3, 1933 1,980,100 Schlumberger Nov. 6,1934 2,033,135 Fay et al Mar. 10, 1936 2,120,670 Hyer June 14, 19382,192,863 Hetzel et al Mar. 5, 1940 2,228,623 Ennis Jan. 14, 19412,246,542 Smith June 24, 1941 2,263,859 Eldredge Nov. 25, 1941 2,282,431Smith et al. May 12, 1942 2,288,876 Arnold July 7, 1942 2,327,658 MillerAug. 24, 1943 2,012,138 Palmer et al Aug. 20, 1935 2,317,632 Miller Apr.27, 1943

